/Engine/Source/Runtime/Engine/Public/Slate/SceneViewport.h
Give the viewport an opportunity to override the navigation behavior. This is called after all the navigation event bubbling is complete and we know a destination.
whether we handled the navigation
virtual bool HandleNavigation ( const uint32 InUserIndex, [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [SWidget](API\Runtime\SlateCore\Widgets\SWidget) > InDestination )